Finite element study of concrete columns with fiber composite jackets

Yi-Ming Lan, Purdue University

Abstract

The need for renewal of existing civil infrastructure has increased significantly in recent years. Consequently, the application of advanced composite materials to these systems, particularly Fiber-Reinforced Plastics (FRP), has received significant attention worldwide. More and more the research community, government organizations, and the industry are devoting their attention to this field. However, major barriers still exist to the infusion of this technology. They include the fact that the structural behavior of new FRP-composite structures is not fully understood and the lack of design criteria for these applications. The current work is intended to contribute to this area of research, in particular to FRP-jacketed concrete column applications. In as such, a relatively sophisticated three-dimensional finite element model has been developed, implemented and tested to study the structural behavior of active and passive confined concrete columns. Part of this study has been conducted using a general-purpose finite element program (ABAQUS). The new FRP material model UMATfrp has been developed based on the classical laminate theory incorporated with the Maximum Stress and Sudden Failure criteria. By modifying and extending an existing concrete model, which is based on the plasticity theory, a new concrete model UMATconc has been developed. This new model has been formulated in strain-space and it includes features such as Drucker-Prager yield and failure surfaces, nonassociated flow rule with nonlinear bounding potential surfaces, and isotropic hardening rule. Moreover, the return mapping integration scheme and the consistent tangent operator have also been formulated in strain space and employed in the present hydrostatic-sensitive plasticity model. It should be noted that most concrete plasticity studies employ the continuum tangent operator. The developed components have then been integrated to simulate the behavior of to FRP-jacketed concrete columns. It has been found that the developed components predict the pre-peak and the post-peak stress-strain behavior in good agreement with experimental results involving unconfined, active and passive confined concrete, as well as different types of concrete. The developed FRP model is capable of describing both pre- and post-failure behavior. It has also been found that the important inelastic behavior of concrete for the current applications is well represented by the present model. This includes strain-hardening-softening behavior, ductile behavior in compression, hydrostatic sensitivity, and volumetric dilation under compressive loading. The return mapping algorithm and the consistent tangent operator developed in this work provide the necessary computational efficiency and stability for the strain-space hydrostatic-sensitive elastoplastic model. Finally, it has been found that for passive confined concrete structures, FRP-jacketed concrete columns in this case, the internal stress interaction diagram can be used to assess the interactive relationships of jacket stresses, confining pressure and concrete stresses, and to further understand the overall structural behavior of these systems. (Abstract shortened by UMI.)

Degree

Ph.D.

Advisors

Sotelino, Purdue University.

Subject Area

Civil engineering

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